Using power from a compressed gas is one of most common approaches to shoot a projectile for an airsoft that shoots a BB bullet (i.e., a 6 mm or 8 mm spherical plastic projectile) or an airgun (such as an air rifle) that shoots a metal projectile. Common compressed gases include propane, green gas (mixture of propane and a very small amount of silicone oil), HFC-134a, carbon dioxide, and the like. Compared with other gases, liquid carbon dioxide stores amazing energy and has an ideal greenhouse effect index (the ability of a gas to absorb thermal energy under the same temperature and the same pressure). This is why carbon dioxide high pressure gas cylinders are widely applied to airguns (e.g., air rifles). Some airsoft guns (for example, air pistols), which are specially designed to withstand high pressure gas, may also use carbon dioxide to shoot a BB bullet.
In the airgun and airsoft industries, gas pressure potential energy is usually stored in a 12 g compressed carbon dioxide gas cylinder for direct use, or gas is injected into a gas storage cavity inside a gun body or a fixed gas tank connected to the gun body by a hand pump, an air compressor or a scuba tank. Although large volume (e.g., 88 g) disposable compressed carbon dioxide gas cylinders are commercially available, they can only be directly used by very few airguns. Therefore, a carbon dioxide adapter designed for the large volume (e.g., 88 g) disposable compressed carbon dioxide gas cylinders is desired, which may safely inject gas to and pressurize the gas storage cavity or fixed gas tank while avoiding leakage of carbon dioxide. In this way, it is convenient for users to use the large volume disposable compressed carbon dioxide gas cylinders for various gas-injection objects including those in the airgun industry.